1. Field of the Invention
This invention relates to a tariff arrangement, preferably but not exclusively for an electricity meter, comprising a microcomputer, a data memory and an interface for the bidirectional transfer of data from and to an external terminal.
2. Description of the Prior Art
A tariff arrangement of the above-mentioned kind is known from Protocol 1987 of the Fifth International Conference on Metering Apparatus and Tariffs for Electricity Supply (JSBN 0 85296346 7 ISSN 0537--9980) pages 86 to 90. In that tariff arrangement, data stored in the data memory can be transferred into a mobile read-out device by way of an optical bidirectional data link to an interface and conversely data can be transferred into the tariff arrangement from the read-out device. In a read-out operation for example the clock time and the calendar are set to the newest state, but it is also possible to alter parameters which serve for tariff configuration. The data link is standarized (DN 66258).
If electricity meters and associated tariff arrangements are covered by the requirement for calibration, those measuring assemblies are sealed after the calibration operation by means of lead seals, thereby ensuring that data which are relevant from the point of view of calibration law can only be altered after the lead seal has been broken. In the case of the above-mentioned tariff arrangement however it is also possible for softward parameters to be varied by way of the optical bidirectional interface. There are objections to allowing such tariff arrangements for calibration because it is not impossible that, in the event of unrecognised errors in the software, data serving for charging purposes could also be varied by way of the interface.